Presently, most durable metallurgical vessel designs employ a two-layer concept wherein the inner layer, the refractory lining, provides heat resistance and the outer layer, or shell, provides the physical strength. The inner layer consists of horizontal courses of bricks bonded together with a suitable refractory mortar; the courses are stacked against the inner surface of the outer layer. Since the bricks are more durable than the mortar, lining failure typically occurs in the mortared joints. This mode of failure must be delayed if there is to be a significant increase in the life of metallurgical vessels.
In the widely used prior art wedge-shaped refractory brick design, the joints between the bricks within one course are radially oriented straight lines. Because of the hoop stress generated in the lining, by the static pressure of the molten metal, the mortar in these joints is subjected to a tensile stress. However, the tensile strength of the mortar is low, only about 1/4 of its shear strength and the applied tensile stress markedly accelerates the deterioration of the mortar. Thus, in this configuration the most common failure occurs as a section of mortar in a joint between two bricks in the same course deteriorates and the molten metal is able to leak through the refractory lining to the outer shell. At this point the entire refractory lining must be replaced even though the bricks themselves may be intact and in relatively good condition.